Hemolytic uremic syndrome (HUS) is a vascular disease with primary damage of the kidneys in which glomerular microcapillaries become occluded with fibrin and platelets. Escherichia coli 0157:H7 is an "emerging infectious disease" responsible for outbreaks of food-borne disease and is the leading cause of HUS and acute renal failure in young children. Most new information on HUS has come from studies related to the E. coli Shiga-like toxin (Stx)- producing dysentery bacteria and the subsequent appearance of HUS those individuals. The long-term goal is to describe, in biochemical terms, the mechanisms by which Stx's and host factors elicit the HUS disease state and to use this knowledge to develop effective preventative or therapeutic intervention modalities. The goal of the present study is to delineate the role of Stx's at the vascular endothelial cell level in the development of HUS. These studies utilize the human renal microvascular endothelial cell type which is believed to be the primary target of Stx's during the development of HUS. The research plan seeks to answer why some endothelial cell types are more sensitive to the Stx's than are others and why human renal endothelial cells are particularly sensitive to Stx2, as they recently demonstrated. The plan consists of four parts: 1) to examine the isoforms of Stx receptor (Gb3) produced by different endothelial cells, 2) to determine the nature of internalization and processing of Stx's by endothelial cells, 3) to study the biochemical pathways utilized by other bacterial and host factors (TNF-alpha & IL 1-beta) to sensitize endothelial cells to the E. coli Stx's, and 4) to identify those endothelial factors that contribute to coagulation in HUS. In summary, this research combines the areas of infectious disease and vascular physiology and has as its primary goal to provide an understanding of the mechanisms underlying the development of renal vascular disease in HUS.